Sisal carpet is considered tough mainly because it is made of sisal fibers. Here are the main reasons:

Fiber Properties: Sisal fibers come from the agave sisal plant, which produces long, hard and strong fibers. These fibers are naturally rough and have a hard texture, which makes the carpet tougher.

Durable: Sisal is known for its durability and resistance to wear and tear. This strength translates into a hard texture, which is one of the reasons it is favored in high-traffic areas.

Weave Construction: The way sisal rugs are woven also adds to their hardness. The tight weave pattern used in sisal rugs not only enhances durability, but also makes the surface denser and harder.

Lack of Cushioning: Unlike rugs made of softer fibers such as wool or synthetics, sisal rugs often have little to no cushioning. The lack of a soft backing material means that the hardness of the fiber is more noticeable.

Natural Characteristics: Sisal fibers do not have the natural elasticity or resilience of some other carpet materials. This rigidity is a natural property of the sisal plant fiber.

While the stiffness of sisal carpet may be seen as a drawback in terms of comfort, it is also a quality that makes it very durable for areas where tough, durable carpet is needed.